4.6.3 Causes of Changes

4.6.3.1 Changes in Snowfall and Surface Melting

For Greenland, modelling driven by reanalyses and calibrated against surface observations indicates recent increases in temperature, precipitation minus evaporation, surface melt water runoff and net mass loss from the surface of the ice sheet, as well as areal expansion of melting and reduction in albedo (Hanna et al., 2005, 2006; Box et al., 2006). High interannual variability means that many of the trends are not highly significant, but the trends are supported by the consistency between the various component data sets and results from different groups. Estimated net snowfall minus melt water runoff includes an increase in the Greenland contribution to sea level rise of 58 Gt yr–1 between the 1961 to 1990 and 1998 to 2003 intervals (Hanna et al., 2005), or of 43 Gt yr–1 from 1998 to 2004 (Box et al., 2006).